It is known to arrange, in the flow path of the air passing through a motor vehicle cooling radiator, a multiplicity of shutters which are mounted for pivoting movement about parallel axes and which are actuated by control means such that they can adopt different angular positions in such a way as to adjust the air flow that passes through the radiator, so optimising the efficiency of the radiator and the operating temperature of the engine. One regulating device of this kind, having pivoting shutters, is known from the specification of French published patent application No. FR 2 191 493A.
It is also known to use control means which include a movable actuating member carrying a number of cam tracks of selected shapes, each of which is adapted to receive a cam element which is fixed in rotation to a corresponding shutter. In regulating devices of this type, the shutters are synchronised so that they all simultaneously have the same angular orientation with respect to the direction of flow of the air stream.
Such an arrangement has certain drawbacks. For example, when the vehicle is running at high speed, the shutters may encounter difficulties in opening or closing, due to the air pressure which is exerted simultaneously on all the shutters. This disadvantage is encountered mainly when all of the shutters are closed, because there is then a large pressure difference between the regions lying respectively upstream and downstream of the shutters with respect to the flow direction of the air stream.
In order to overcome this pressure difference, it is necessary to provide control means which are sufficiently powerful, and which are therefore cumbersome and expensive in terms of energy consumption.